Arrays can be passed down to functions like other single variables. We use them by their name as arguments when we call the function. The parameter list of the function must indicate the fact that a parameter is an array by augmenting the [ ] at the end of the one dimensional arrays. In one-dimensional arrays the actual size does not have to be given. In case of two-dimensional arrays we recommend that you give the size of the array in both dimensions.

NOTE: Arrays are always passed by name. In other words if we change the array in the function, then this change reflects back to the calling function.

Read the explanations provided for the example .

 /*
      J.Y.Kazakia October 14,1998
 
This example illustrates the following:
 
1) Arrays in C++.
 
2) Arrays passed to a function return their updated values
to the main.
 
Here a set of four numbers is passed to a function called 
square_them first individually and then as an array. The
results in both cases are then compared. The function forms
the squares of the numbers.
 
                                */
#include <iostream.h>
#include <fstream.h>

  /* function prototypes */
 
void square_them ( float a, float b, float c, float d,float array[]);      

ofstream out( "6ex3rep.txt" , ios:: out);
 
main ( )
 
{

float a, b, c, d;
float array[4];
int i;
 
a = 1.1;
b = 2.2;
c = 3.3;
d = 4.4;

for ( i = 0; i <= 3; i++)
array [ i ] =(1+ i) +( i +1 ) / 10.;
 
/* this is equivalent to writing: array[0] = 1.1;
                                  array[1] = 2.2;
                                  array[2] = 3.3;
                                  array[3] = 4.4;

   Print before you call the function    */
out << " \n\n\n  Printing before  calling the function";
out << endl << endl;
out << " a =" << a << " b =" << b << " c =" << c ;
out <<" d =" << d ;
 
for ( i = 0; i <= 3; i++)
out <<"\n\n   array["<<i<<"] = "<<array[i];

/*****************************************
 
   Call the function
 
*****************************************/
 
square_them( a, b, c, d, array );

/*   Print after  you call the function    */
 
out << " \n\n\n  Printing after  calling the function";
out << endl << endl;
out << " a =" << a << " b =" << b << " c =" << c ;
out <<" d =" << d ;
 
for ( i = 0; i <= 3; i++)
out <<"\n\n   array["<<i<<"] = "<<array[i];
 
 
}

 void square_them( float a, float b, float c, float d, float u[])
 
{
int i;
 
a = a * a;
b = b * b;
c = c * c;
d = d * d;
 
i=0;
while (i <= 3)
  {
     u[i] = u[i] * u[i];
     i++;

/*   Print from within the function    */
 
out << " \n\n\n  Printing from within the function";
out << endl << endl;
out << " a =" << a << " b =" << b << " c =" << c ;
out <<" d =" << d ;
 
for ( i = 0; i <= 3; i++)
out <<"\n\n   array["<<i<<"] = "<< u[i];
 
}

THE OUTPUT IS:
 
  Printing before  calling the function
 
 a =1.1 b =2.2 c =3.3 d =4.4
 
   array[0] = 1.1
 
   array[1] = 2.2
 
   array[2] = 3.3
 
   array[3] = 4.4 
 
 
  Printing from within the function
 
 a =1.21 b =4.84 c =10.89 d =19.36
 
   array[0] = 1.21
 
   array[1] = 4.84
 
   array[2] = 10.89
 
   array[3] = 19.36 
 
 
  Printing after  calling the function
 
 a =1.1 b =2.2 c =3.3 d =4.4
 
   array[0] = 1.21
 
   array[1] = 4.84
 
   array[2] = 10.89
 
   array[3] = 19.36
 
 
   */